A fragile balance at synapses: new evidence supporting a role for FMRP in homeostatic plasticity.

a Crect/RosaYFP mouse, in which Cre recombination leads to RosaYFP expression only in cells of ectodermal origin. In the olfactory epithelium, YFP expression (green) was detected in the majority of olfactory sensory neurons (colabeled in red) and sustentacular cells (green only). In the lamina propria, olfactory axons (red/green) and Bowman’s glands (green only) were positive for ectodermal YFP labeling, whereas olfactory ensheathing cells (detected by blue nuclear DAPI staining surrounding the axons of olfactory sensory neurons and Bowman’s glands) were YFP negative, indicating a nonectodermal origin. For more information, see the article by Forni et al. in this issue (pages 6915– 6927). i This Week in The Journal